1. Field of the Invention
The present invention relates to a backlight device having one or more optical sheets and a display apparatus such as a liquid crystal display apparatus.
2. Description of the Related Art
Liquid crystal display apparatuses can be configured to have a larger display screen, lighter weight, a shape with a lower profile, lower electricity consumption, etc., than cathode-ray-tube (CRT) display apparatuses. Therefore, they are now used as television receivers or various displays along with, for example, self-luminous plasma display panels (PDPs) and the like.
Typically, a liquid crystal display apparatus has two transparent substrates, which can be of any size, with liquid crystal enclosed therebetween. By applying a voltage, the orientation of liquid crystal molecules is changed to cause light transmittance to change, whereby predetermined images and the like are optically displayed. Because liquid crystal itself does not emit light, a liquid crystal display apparatus has, for example, a backlight device functioning as a light source on the back of a liquid crystal panel. Such backlight device has, for example, a primary light source, a light-guiding plate, a reflective film, a lens sheet, and a diffusing film, and supplies display light over the entire surface of the liquid crystal panel. In such backlight devices, a cold-cathode fluorescent lamp (CCFL) has been used as the primary light source, in which mercury or xenon is enclosed in a fluorescent tube. CCFLs have, however, problems in that they have a low light-emitting luminance, a short life, and a poor uniformity of illuminance due to existence of a low luminance region on the cathode side.
Recently, a light-emitting diode (hereinafter referred to as an LED) backlight device has been attracting attention as an alternative to CCFLs. In such an LED backlight device, a number of red, green, and blue LEDs, which represent the three primary colors of light, are aligned two-dimensionally behind the back surface of the diffusing film to produce white light. The LED backlight device has a low power consumption and enables high-luminance display with a large liquid crystal panel.
Backlight devices have a variety of optical components disposed between the light source unit and the transmissive liquid crystal panel in order to uniformize luminance, chromaticity, and the like over the entire surface of the display. These optical components convert the characteristics of display light emitted from a light source and make the display light uniform. Examples of such optical components include an optical functional sheet block, a light-diffusing/guiding plate, a light-diffusing plate, and a reflective sheet.
As disclosed in, for example, Japanese Unexamined Patent Application Publication Nos. 2006-58484 and 2005-242270, thinner examples of these optical components are typically held in a hanging state, in which a supporting member penetrates through an opening provided in the component to fix the position of the component or so that the component does not become detached from a predetermined attachment position by vibration.